add fuzz target for azihsm_ddi_tbor_codec::RequestEncoder

[zimmy87]

No description provided.

[Copilot]

Pull request overview

Adds a new cargo-fuzz target to exercise azihsm_ddi_tbor_codec::RequestEncoder with randomized sequences of TOC-builder operations, aiming to catch panics/logic errors in the TBOR request encoding surface.

Changes:

• Introduces a libfuzzer-sys fuzz target that chains RequestEncoder builder calls and attempts finish().
• Adds a fuzz/ Cargo package with the fuzz binary configuration and local .gitignore.
• Registers fuzz/ as a workspace member.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
fuzz/fuzz_targets/ddi/tbor/fuzz_tbor_encoder.rs	New libFuzzer target that drives RequestEncoder through arbitrary operation sequences.
fuzz/Cargo.toml	New fuzz crate manifest defining the fuzz binary and dependencies.
fuzz/.gitignore	Ignores fuzz build/corpus/artifact outputs.
Cargo.toml	Adds fuzz/ to the workspace members list.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Suppressed comments (2)

Cargo.toml:39

• libfuzzer-sys is Linux-only (it depends on LLVM libFuzzer/sanitizer support), but adding the fuzz crate as a workspace member means cargo xtask precheck --clippy/CI will attempt to build & clippy it on Windows as well (and this repo runs precheck clippy on Windows). That will likely break cross-platform CI unless the fuzz package/targets are excluded from precheck or made non-building on non-Linux targets.

  "fuzz",

ddi/tbor/codec/src/encode.rs:150

• New early validation in buffer_reserve changes the error surface (e.g., BufferTooSmall/DataOffsetOverflow can now be returned from buffer_reserve rather than only being discovered later). There are existing integration tests for encoder error paths; please add a regression test that exercises the new buffer_reserve failure case (e.g., reserve enough bytes to exceed the staging area) to prevent future reintroduction of the bug this change fixes.

        // Validate that the staging area can accommodate the reserved bytes.
        let _ = self.stage_range(len)?;
        self.data_offset += len;
        self.check_offset_overflow()?;
        Ok(self)

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

Suppressed comments (1)

ddi/tbor/codec/src/encode.rs:149

• buffer_reserve(0) should not require the staging area to fit in buf. With the new unconditional stage_range(len)? check, callers with a small buffer (large enough for header+TOC but smaller than stage_base()) can no longer encode a zero-length buffer entry, even though no staged bytes will ever be copied in finish when len == 0 (data_offset remains unchanged). This is also inconsistent with padding, which only calls stage_range when len > 0.

        // Validate that the staging area can accommodate the reserved bytes.
        let _ = self.stage_range(len)?;
        self.data_offset += len;
        self.check_offset_overflow()?;

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Suppressed comments (3)

fuzz/fuzz_targets/ddi/tbor/fuzz_tbor_request_encoder.rs:12

• Unused import: libfuzzer_sys::arbitrary isn’t referenced in this target and will trigger an unused_imports warning when compiling the fuzz crate.

use libfuzzer_sys::arbitrary;

fuzz/fuzz_targets/ddi/tbor/fuzz_tbor_response_encoder.rs:12

• Unused import: libfuzzer_sys::arbitrary isn’t referenced in this target and will trigger an unused_imports warning when compiling the fuzz crate.

use libfuzzer_sys::arbitrary;

fuzz/fuzz_targets/common.rs:8

• Unused import: libfuzzer_sys::arbitrary isn’t referenced in this module and will trigger an unused_imports warning when compiling the fuzz crate.

use libfuzzer_sys::arbitrary;

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Suppressed comments (3)

ddi/tbor/codec/src/encode.rs:147

• let _ = self.stage_range(len)?; is a no-op binding; calling the method directly is clearer and avoids suggesting the result is intentionally dropped for side effects.

        // Validate that the staging area can accommodate the reserved bytes.
        let _ = self.stage_range(len)?;
        self.data_offset += len;

fuzz/fuzz_targets/ddi/tbor/fuzz_tbor_request_view.rs:26

• In fuzzing builds (typically --release), these accessor calls can be optimized away because their results are unused and the methods are pure/#[inline], which reduces the value of the fuzz target. Use std::hint::black_box to ensure the code paths are actually exercised.

fuzz_target!(|data: &[u8]| {
    if let Ok(view) = RequestView::parse(data) {
        let _ = view.version();
        let _ = view.opcode();
        let _ = view.toc_count();

fuzz/fuzz_targets/ddi/tbor/fuzz_tbor_response_view.rs:28

• In fuzzing builds (typically --release), these accessor calls can be optimized away because their results are unused and the methods are pure/#[inline], which reduces the value of the fuzz target. Use std::hint::black_box to ensure the code paths are actually exercised.

fuzz_target!(|data: &[u8]| {
    if let Ok(view) = ResponseView::parse(data) {
        let _ = view.version();
        let _ = view.flags();
        let _ = view.fips_approved();
        let _ = view.status();